The inhibition by lysine of the activation of the first component of complement, C1.

Lysine prevented the activation of Cl at low ionic strength or by heat aggregated IgG (aggIgG) measured by the hydrolysis of acetyl tyrosine ethyl ester (ATEe) by Cls. When serum was mixed with aggIgG, complement was activated and consumed. If lysine was present in the serum containing aggIgG, the activation of complement, thus its consumption, was inhibited in a dose-response manner. Cl haemolysis assay which measures the Cl activity to interact with EA (erythrocytes bound with antibody) was used to study the effects of lysine. The results indicate that 50% of Cl haemolysis was inhibited at 3 mM of lysine. Crossed immunoelectrophoresis indicates that Cl in the serum was activated by aggIgG, but Cls thus formed seemed to be soon complexed with Cl inactivator. The presence of lysine prevented the conversion of Cls to Cls completely. It might be possible that lysine binds with the binding sites on Clq, thus preventing the interaction of Clq and C gamma 2.